• Title/Summary/Keyword: Straight tube

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Manufacturing and Temperature Measurements of a Sodium Heat Pipe

  • Lee, Byeong-In;Lee, Seong-Hong
    • Journal of Mechanical Science and Technology
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    • v.15 no.11
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    • pp.1533-1540
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    • 2001
  • A high-temperature sodium stainless steel heat pipe was fabricated and its performance has been investigated. The working fluid was sodium and it was sealed inside a straight tube container made of stainless steel. The amount of sodium occupied approximately 20% of the total volume of the heat pipe and its weight was 65.7gram. The length of a stainless steel container is 1002mm and its outside diameter is 25.4mm. Performance tests were carried out in a room air condition under a free convective environment and the measured temperatures are presented. The start-up behavior of the heat pipe from a frozen state was investigated for various heat input values between 600W and 1205W. In steady state, axial temperature distributions of a heat pipe were measured and its heat transfer rates were estimated in the range of vapor temperature from 50$0^{\circ}C$ to 63$0^{\circ}C$. It is found that there are small temperature differences in the vapor core along the axial direction of a sodium heat pipe for the high operating temperatures. But for the range of low operating temperatures there are large temperature drops along the vapor core region of a sodium heat pipe, because a small vapor pressure drop makes a large temperature drop. The transition temperature was reached more rapidly in the cases of high heat input rate for the sodium heat pipe.

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Development of a Cardiovascular Simulator with Cardiovascular Characteristics (혈관계의 특성이 반영된 심혈관계 시뮬레이터의 개발)

  • Lee, Ju-Yeon;Shin, Sang-Hoon
    • The Journal of the Society of Korean Medicine Diagnostics
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    • v.16 no.3
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    • pp.33-40
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    • 2012
  • Objectives: Existing cardiovascular simulators are used to evaluate artificial organs such as artificial hearts, prosthetic valves, and artificial blood vessels, and pulses are typically triggered using artificial hearts. However, the forms of pulse waves vary according to the location of arteries, and for precise assessment of artificial blood vessels, the development of simulators that generate diverse pressure pulse waves is necessary. This study developed a novel cardiovascular simulator that generates different forms of pulse waves. Methods: This simulator consists of a stepping motor, a slider-crank mechanism that transforms the rotation movement of a motor into the straight-line motion of a piston, a piston that generates pulsatile flows, a water tank that supplies fluids, an elastic tube made of silicon, and a device that adjusts the terminal resistance of fluids. Results & Conclusion: This study examined motor rotation and its operation under conditions similar to the physiological conditions of the heart. The simulator developed in this study produced diverse forms of waves, and the generated pressure waves well satisfied physiological conditions.

Heat Transfer and Frictions in the Convergent/divergent Channel with Λ/V-shaped Ribs on Two Walls

  • Kim, Beom-soo;Lee, Myung-sung;Ahn, Soo-whan
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.3
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    • pp.395-402
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    • 2017
  • The local heat transfer and total pressure drops of developed turbulent flows in the ribbed rectangular convergent/divergent channels with ${\Lambda}/V-shaped$ ribs have been investigated experimentally. The channels have the exit hydraulic diameter ($D_{ho}$) to inlet hydraulic diameter ($D_{hi}$) ratios of 0.67 for convergence and 1.49 for divergence, respectively. The ${\Lambda}/V-shaped$ ribs with three different flow attack angles of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ are manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (S) to height (e) of 10 on the walls. Thermal performances of the ribbed rectangular convergent/divergent channels are compared with the smooth straight tube under identical pumping power. The results show that the flow attack angle of $45^{\circ}$ with ${\Lambda}-shaped$ rib has the greatest thermal performance at all the Reynolds numbers studied in the convergent channel; whereas, the flow attack angle of $60^{\circ}$ with V-shaped rib has the greatest thermal performance over Reynolds number of 30,000 in the divergent channel.

Experiment Research of Autonomous Driving Valve for Pulse Detonation Rocket Engine

  • Matsuoka, Ken;Yamaguchi, Hiroyuki;Nemoto, Toyoshi;Yageta, Jun;Kasahara, Jiro;Yajima, Takashi;Kojima, Takayuki
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.419-426
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    • 2008
  • As pulse detonation engine(PDE) does not need compression mechanisms such as compressors because self-sustained detonation waves are able to compress propellant gases by their incident shock waves, the PDE can have a simple straight-tube structure. In this study, we propose an autonomous driving valve system of the PDE, which fill premixed gases into the PDE tubes at high frequency with high mass flow rate. The proposed valve is composed of only three parts: a piston, a cylinder, and a spring. This valve system can produce intermittent flow at high mass flow rate, and also can keep stable reciprocal motion by using the propellant-gas enthalpy. When the cylinder content product is assumed to be constant, experimental results of the mass flow rate were approximately equal to the calculation model. We confirmed the autonomous driving valve performance by experiments, and concluded that this extremely simple valve with no electrical power and controller can be used as the PDE propellant supply system.

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Influence of Wall Motion and Impedance Phase Angle on the Wall Shear Stress in an Elastic Blood Vessel Under Oscillatory Flow Conditions (맥동유동하에 있는 탄성혈관에서 벽면운동과 임피던스 페이즈앵글이 벽면전단응력에 미치는 영향)

  • 최주환;이종선;김찬중
    • Journal of Biomedical Engineering Research
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    • v.21 no.4
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    • pp.363-372
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    • 2000
  • The present study investigated flow dynamics of a straight elastic blood vessel under sinusoidal flow conditions in order to understand influence of wall motion and impedance phase angle(time delay between pressure and flow waveforms) on wall shear stress distribution using computational fluid dynamics. For the straight elastic tube model considered in the our method of computation. The results showed that wall motion induced additional terms in the axial velocity profile and the pressure gradient. These additional terms due to wall motion reduced the amplitude of wall shear stress and also changed the mean wall shear stress. Te trend of the changes was very different depending on the impedance phase angle. As the wall shear stress increased. As the phase angle was reduced from 0$^{\circ}$to -90$^{\circ}$for ${\pm}$4% wall motion case, the mean wall shear stress decreased by 10.5% and the amplitude of wasll shear stress increased by 17.5%. Therefore, for hypertensive patients vulnerable state to atherosclerosis according to low and oscillatory shear stress theory.

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Finestructure and Function of Vas deferens in a freshwater Prawn Macrobrachium nipponense (징거미새우, Macrobrachium nipponense 수정관의 미세구조와 기능)

  • Kim Dae Hyun;Lee Jae Young;Jung Jee Hyun;Kang Jung Ha;Lee Bok Kyu;Han Chang Hee
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.35 no.4
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    • pp.424-430
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    • 2002
  • Vas deferens is a long tube and could be divided into four regions as its morphological characters: a short and slender proximal region, a convoluted region, a straight and more thick distal region, and an ejaculatory duct, It is connected with the posterior outer horns of the testis and runs to the gonopores opened on the coxa of the fifth walking legs, The proximal region consists almost entirely of simple cuboidal epithelial cells, $12\~28{\mu}$m in height, surrounded by a thin basal membrane. A small aggregation of high cuboidal epithelium is obsened from one side of the proximal region. The convoluted and distal region is composed of two kinds of epithelial cells; high cuboidal epithelial cells, $40\~120{\mu}m$ in height located in dorsal portion and simple cuboidal epithelial cells of $12\~28{\mu}$m in height located in ventral and lateral portion. The ejaculatory duct is surrounded with two kinds of muscle layers, inner longitudinal and outer circular muscle fibers, The lumen is lined with high and simple cuboidal epithelium in almost equal proportions. The proximal region contains mature sperm and basophilic substances. The eosinophilic substances appeared newly going toward the convoluted region and are laid along simple cuboidal epithelial cell layer. Tube-like content (spermatophore) of the vas deferens is ejaculated from a pair of genital pores at mating. Two masses of the content fuse together side by side and are usually deposited on the female thorax between the second and fourth or fifth pereiopods, The spermatophore formed measures $2.7\~4.0$ mm in length and $1.5\~2.7$ mm in width.

Structure on the Ventral Process and the Ovipositor of a Korean Oily Bitterling, Acheilognathus koreensis (Pisces, Cyprinidae), in Relation to Spawning Season (산란시기의 칼납자루 Acheilognathus koreensis (잉어과)의 배측융기와 산란관의 구조)

  • Park, Jong-Young;Kim, Ik-Soo
    • Korean Journal of Ichthyology
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    • v.18 no.1
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    • pp.27-35
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    • 2006
  • During spawning season of female in a Korean oily bitterling, Acheilognathus koreensis, the ventral region near the base of the pectoral fin becomes to be protruded outward of body and enlarged. This ventral process consists of both organs as rectum (vent) and inner ovipositor. The rectum consists of mucosa, lamina propria-submucosa, muscularis, and squamous epithelial layer (peritoneum=serosa) surrounding them. The mucosa contains numerous mucous cells meaning acid mucopolysaccharides in nature. The inner ovipositor is similar to that of the rectum, but the mucosa have no mucous cell, unlike that of the rectum. Whereas, the outer ovipositor has a straight and long tube which are not connected with the ventral process any more. The outer ovipositor was similar to the structure of the inner ovipositor in the ventral process. However, the outer ovipositor has no muscularis, and consists of three layers: mucosa, lamina propria-submucoa, and squamous epithelia. The outer ovipositor without the muscularis seems serves as a tube that eggs discharged from the outer ovipositor allow to send inside mussel, unlike that of the inner ovipositor performing rhythmic contractions of the layers of the muscularies for propelling to the matured oocytes to the outer ovipositor.

Interpretation and Analysis of Seismic Crosshole Data: Case History (탄성파 토모그래피 단면측정 데이터 분석 및 해석: 현장응용 사례)

  • Kim Jung-Yul;Kim Yoo-Sung;Hyun Hye-Ja
    • Geophysics and Geophysical Exploration
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    • v.1 no.1
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    • pp.31-42
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    • 1998
  • Recently crosshole seismic tomography has come to be widely used especially for the civil engineering, because it can provide more detail information than any other surface method, although the resolution of tomogram will be inevitably deteriorated to some extent due to the limited wavefield aperture on the nonuniqueness of traveltime inversion. In addition, our field sites often consist of a high-velocity bed rock overlain by low-velocity rock, sometimes with a contrast of more than 45 percent, and furthermore the bed rock is folded. The first arriving waves can be then the refracted ones that travel along the bed rock surface for some source/receiver distances. Thus, the desirable first arrivals can be easily misread that cause severe distortion of the resulting tomogram, if it is concerned with (straight ray) traveltime inversion procedure. In this case, comparision with synthetic data (forward modeling) is a valuable tool in the interpretation process. Besides, abundant information is contained in the crosshole data. For instance, examination of tube waves can be devoted to detecting discontinuities within the borehole such as breakouts, faults, fractures or shear zones as well as the end of the borehole. Specific frequency characteristics of marine silty mud will help discriminate from other soft rocks. The aim of this paper is to present several strategies to analyze and interpret the crosshole data in order to improve the ability at first to determine the spatial dimensions of interwell anomalies and furthermore to understand the underground structures. To this end, our field data are demonstrated. Possibility of misreading the first arrivals was illustrated. Tube waves were investigated in conjunction with the televiewer images. Use of shot- and receiver gathers was examined to benefit the detectabilities of discontinuities within the borehole.

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PIV Measurement of Pulsatile Flows in 3D Curved Tubes Using Refractive Index Matching Method (3차원 곡관에서의 굴절률 일치법을 이용한 맥동 유동의 PIV 측정)

  • Hong, Hyeon Ji;Ji, Ho Seong;Kim, Kyung Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.8
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    • pp.511-517
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    • 2016
  • Three-dimensional models of stenosis blood vessels were prepared using a 3D printer. The models included a straight pipe with axisymmetric stenosis and a pipe that was bent $10^{\circ}$ from the center of stenosis. A refractive index matching method was utilized to measure accurate velocity fields inside the 3D tubes. Three different pulsatile flows were generated and controlled by changing the rotational speed frequency of the peristaltic pump. Unsteady velocity fields were measured by a time-resolved particle image velocimetry method. Periodic shedding of vortices occurred and moves depended on the maximum velocity region. The sizes and the positions of the vortices and symmetry are influenced by mean Reynolds number and tube geometry. In the case of the bent pipe, a recirculation zone observed at the post-stenosis could explain the possibility of blood clot formation and blood clot adhesion in view of hemodynamics.

Normal and Abnormal Development of the Heart (심장의 정상 및 이상발생)

  • Seo, Jeong-Uk;Choe, Jeong-Yeon;Seo, Gyeong-Pil;Ji, Je-Geun
    • Journal of Chest Surgery
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    • v.29 no.2
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    • pp.136-146
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    • 1996
  • Studies on normal human embryos and on malformed human hearts have been two main sources of the information on the developmental cardiology, Recent advances in the biological technology has opened a new era and descriptive embryology is being shifted into dynamic developmental biology. In this review, we discuss the current understanding on the cardiac embryology relevant to clinical practices of pediatric cardiology. Classical cardiac embryology starts with understanding on five segments of a straight heart tube : the sinus venosus, the primitive atria, the embryonic left ventricle, the embryonic right ventricle and the truncus arteriosus. Key steps in the normal morphogenetic process are the complex spiral septation of ventriculoarterial junction and two jumping connections : between the embryonic right atrium and embryonic right ventricle, and between the embryonic left ventricle and the aorta. Only after these two steps are successfully completed, the third fetal stage tak s place, when myocardial growth and remodeling take place There are two outstanding progresses on the cardiac embryology during recent five-year period. One is immunohistochemical mapping of the conduction system in the developing heart and the other is the understanding on the neural crest cell migration followed by molecular detection of the microdeletion of chromosome 22. A balanced progress of classical morphological studies, modern biological technics and advanced clinical medicine is an urgent task for doctors and scientists dealing with children with sick hearts.

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